Fuel Monitoring and Telematics: Stopping Fuel Theft in a Fleet

How telematics catches fuel theft

Fuel goes missing in three ways: draining from the tank, fuelling that never reaches the vehicle (there is a receipt but the tank level did not rise) and excess consumption from idling, unauthorised trips or faults. No single data source covers all three, so monitoring is built on cross-checks:

• a fuel level sensor shows how much fuel is in the tank;
• the CAN bus provides on-board computer data on consumption, RPM and mileage;
• a GPS tracker shows where and when the vehicle was parked or moving;
• fuel cards show where, when and how much was fuelled according to receipts.

The monitoring platform puts them on a single timeline and looks for mismatches.

Fuel level sensors

The most common option is a capacitive immersion sensor: a measuring tube is installed in the tank and reports the level to the tracker. What matters during installation:

• Tank calibration. Tanks have irregular shapes, so the sensor is calibrated by filling fuel in portions and recording readings. Without a calibration table, the litres will be wrong.
• Filtering. Fuel sloshes while driving; the tracker or platform smooths readings, otherwise every turn looks like a drain.
• Sealing the sensor and connectors, and monitoring power loss — an attempt to disconnect the sensor is an event in itself.
• Two sensors for long or dual tanks.

The vehicle's stock fuel gauge, read via CAN, is usually less accurate than a dedicated sensor — not always enough for drain detection.

CAN-bus data

Through a contactless reader or a direct CAN connection, the tracker receives total fuel used, engine RPM, engine hours, speed and fault codes. This lets you:

• compare on-board consumption with the change in tank level;
• measure idling — engine running, zero speed;
• spot aggressive driving and faults that inflate consumption.

Available parameters depend on make and model, so check compatibility with your fleet before buying hardware.

Fuel card reconciliation

Fuel card transactions are loaded through the issuer's API or exports and matched against tracker data:

Accurate reconciliation requires correctly linking each card to a vehicle or driver and aligning time zones across sources.

Drain alerts

A drain is a sharp level drop not explained by driving. A typical rule: a drop above a threshold within a short period while the vehicle is stationary, with the engine off or idling. The threshold is tuned to the tank and sensor noise.

To make alerts useful rather than annoying:

• send them to the responsible person via Telegram or SMS with a map, time and level chart;
• filter false positives: parking on a slope, hard braking, temperature swings;
• require a response: each event is closed with a comment — confirmed, false, under review.

Reports that reveal anomalies

• Standard vs actual consumption per vehicle and driver for a period.
• Fuelling and drains with a map and level chart.
• Idling — time and fuel burned without moving.
• Comparison of similar vehicles on similar routes: outliers are the first candidates for review.
• Card reconciliation — a list of transactions with mismatches.

Reports are most valuable when their data flows onward: into accounting to write off fuel based on actual use, and into payroll if driver bonuses are tied to fuel savings.

How to roll it out

1. Start with a pilot on a few vehicles of different types.
2. Calibrate tanks and check reading stability over a couple of weeks.
3. Connect fuel cards and set up alert rules.
4. Assign an owner for reviewing events and a clear procedure.
5. Only then scale to the whole fleet.